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Effects of eye muscle proprioceptive activation on eye position in normal and exotropic subjects.

BACKGROUND: Activation of muscle spindles by vibration of eye muscles is known to induce illusory movements of fixated targets, but the effects on eye position have not been studied, either in normal subjects or in patients with exotropia. METHODS: Eye position was recorded from the covered, non-dominant eye with an infrared system in 11 subjects with normal eyes and binocular vision and in 10 patients with exotropia and abnormal binocular function. Activation of eye muscle spindles was done by vibration at 70 Hz of the inferior and lateral rectus muscles of the dominant eye, fixating a light-emitting diode in subdued light. RESULTS: Vibratory activation of proprioceptors in the inferior rectus muscle induced an eye movement mainly directed upward in both normal and exotropic subjects. The magnitude of the movement was on average 2.7 deg in normals and 2.4 deg in exotropes. Lateral rectus vibration induced a movement that was mainly temporally directed (abduction) of an average 2.1 deg in normal subjects, but a nasally directed (adduction) movement of 4.2 deg in exotropic subjects. In normal subjects the eye movement is of the same direction as the earlier reported visual illusory movements induced by the same type of proprioceptive activation, but in exotropic subjects the movements is in the opposite direction. CONCLUSIONS: Proprioceptive activation of eye muscles affects eye position, and the results also indicate that signals from eye muscles are processed differently in normals and strabismics, probably depending on the level of binocular function.

Adult↗

Corneal calcification after chemical eye burns caused by eye drops containing phosphate buffer.

PURPOSE: Chemical burns with calcium containing corrosives as well as irrigation with phosphate buffer solutions after eye burns bear the risk of corneal calcification. The aim of this study was to evaluate the correlation between the occurrence of corneal calcification after chemical injuries and the usage of phosphate buffer containing local therapeutics. METHODS: We reviewed the data of 179 patients who have been treated in the University Eye Clinic Aachen, Germany, between 1941 and 2000. Only when the corrosive did not contain calcium and when the initial irrigating solution did not contain phosphate buffer, respectively, were patients included in the study. The cases were analyse, if the patient was treated with phosphate buffer containing eye drops/ointment during the first 7 days of hospitalization or as an out-patient, and if corneal calcification was visible by slit-lamp examination during the follow-up. Statistical analysis was performed using Fischer's exact test. RESULTS: 152 eyes were included. From 63 eyes treated with phosphate buffer containing eye drops, 31 eyes (49%) developed corneal calcification. From 89 eyes treated without phosphate buffer containing eye drops, only 23 eyes (26%) developed corneal calcification. The two-sided p-value of Fischer's exact test is 0.0036. CONCLUSION: During follow-up after chemical eye burns, eye drops containing phosphate buffer double the risk of corneal calcification. We recommend avoiding these agents in order to prevent the burned cornea from additional opacity. Substances containing phosphate buffer are listed in this article.

Buffers↗

Eye care utilization by older Americans: the SEE Project. Salisbury Eye Evaluation.

OBJECTIVE: To determine eye care utilization patterns among older Americans, particularly characterizing those who sought different types of providers, and the predictive factors for seeking eye care services in general and among those with diabetes and those with visual loss. DESIGN AND PARTICIPANTS: The SEE Project, a population-based survey of 2520 persons aged 65 to 84 in Salisbury, Maryland, provided cross-sectional data on eye care use. Questions on eye care use, demographics, medical history, and other factors were asked on the home interview. MAIN OUTCOME MEASURES: Use of an eye care provider in the previous year, with additional outcomes of use of different types of eye care providers. RESULTS: Blacks were significantly less likely to see any type of eye care provider over 1 year: 50% versus 69% among whites. Those who reported having a vision problem, those with more education, and those in the older age groups were significantly more likely to see either an ophthalmologist or an optometrist. Diabetes and driving a car were predictive factors for seeing an ophthalmologist but not for seeing an optometrist. Self-report of diabetes and eye care problems, and being a current driver, were predictive of seeing an eye care professional among those with visual impairment. CONCLUSIONS: Although blacks are known to be at greater risk for several age-related eye diseases, they are much less likely to see an eye care provider. Interventions that remove barriers to eye care services should be considered.

Aged↗

A test eye for wavefront eye refractors.

PURPOSE: A multi-site study was conducted to test feasibility of a modified automatic refractor style test eye as a test device for wavefront refractors of various types and to determine whether a) they could be measured and b) when measurements could be made, to see if they were similar. This study did not attempt to assess which instrument most accurately measures the aberrations of the test eye or human eye. METHODS: Three automatic refractor style test eyes were modified for use as test devices for wavefront refractors. One had a simple spherical front surface, and two had additional aberrations added. The test eyes and holder were circulated to 11 test sites where attempts were made to measure them with eight different wave-front refractor systems. RESULTS: Eight (100%) of the eight wavefront refractor systems tested successfully measured the test eyes. The systems did not give similar results for the same test eye. In some cases, coma was reported where none was present. Differences in reported defocus values reflect different approaches for compensating for the dispersion of the eye. A corneal topography system could measure and recognize the aberrations of the test eyes as well as the wavefront refractor systems tested. Interferometry, on the other hand, did not prove to be a successful method to assess the surface of the test eyes. CONCLUSIONS: The test eye design may be used as a test device for wavefront refractor systems. This type of test eye can detect systematic differences between various wavefront refractors and can serve as a useful calibration and comparison tool.

Diagnostic Techniques, Ophthalmological↗

[New determinations of the eye rotation center and criteria for the formation of its membrane in terms of the floating eye model and experimental support of the latter].

It is well known that the eye is a phylogenetically stabilized body with rotation properties. The eye has an elastic cover and is filled with uniform fluid. According to the theory of covers and other concepts on the configuration of turning fluid mass we concluded that the eyeball has an elliptic configuration. Classification of the eyeball is here presented with simultaneous studies of the principles of the eye situation. The parallelism between the state and different types of heterophory and orthophory was studied. To determine normal configuration it is necessary to have in mind some principles of achieving advisable correct situation of the eye in orbit. We determined the centre of the eye rotation and showed that it is impossible to situate it out of the geometrical centre of the eyeball. It was pointed out that for adequate perception the rotation centre must be situated on the visual axis. Using the well known theory of floating we experimentally determined that the centre of the eye rotation lies on the level of the floating eye, just on the point of cross of the visual line with the optical axis. It was shown experimentally on the basis of recording the eye movements in the process of eyelid closing that weakening of the eye movements is of gravitational pattern and proceeds under the action of stability forces, which directly indicates the floating state of the eye. For the first time using the model of the floating eye it was possible to show the formation of extraeye vacuum by straining the back wall. This effect can be obtained without any difficulty, if the face is turned down. The role of negative pressure in the formation of the eye ametropy, as well as new conclusions and prognostications about this new model are discussed.

Eye↗

[Study on human eye movements induced by prolonged eye closure and lid opening--report 2. Closing and opening of eyelids].

The eye movement during prolonged eye closure and the following eye opening has not been studied precisely. In the present study we evaluated the eye movement during prolonged eye closure and the following eye opening using a magnetic search oil method. In a bright room, the exact moment of recognizing a visual target during eye opening could not be determined. Therefore, other conditions were used to elucidate the precise relationship between the presence and lack of visual input during eye opening. Eye movement during eye opening was accomplished in three phases. The first phase had rapid movements like visually guided saccades toward the imaged target. The second phase had slow movements and drift toward the imaged target, and the final eye position was reached within 3 degrees from the target from 5 different gaze directions. The third phase was final visually evoked corrective saccades and the subjects found the target. We discuss the origin of these eye movements.

Adult↗

Risk of age-related macular degeneration in eyes with macular drusen or hyperpigmentation: the Blue Mountains Eye Study cohort.

OBJECTIVE: To quantify the 5-year risk of age-related macular degeneration (AMD) in eyes with different macular drusen characteristics (ie, size, type, location, and total area) or hyperpigmentation in a population-based cohort. METHODS: The Blue Mountains Eye Study examined 3654 residents during 1992-1994; 2335 (75.1% of survivors) were reexamined during 1997-1999. Retinal photographs were graded using the Wisconsin Age-Related Maculopathy Grading System. Incident AMD lesions were defined by development of neovascular AMD or geographic atrophy in eyes without these lesions at baseline (eyes at risk). Age-adjusted relative risks (RRs) were determined. Generalized estimating equation models were used to estimate odds ratios, adjusting for the correlation between eyes and other AMD risk factors. Main Outcome Measure Incidence of AMD. RESULTS: Of the 4634 eyes at risk, 52 (1.1%) developed neovascular or atrophic AMD lesions over 5 years. In right eyes, presence vs absence of the following macular signs predicted AMD: drusen that were 125 micro m or larger (13.9 vs 0.6%; age-adjusted RR, 5.7; 95% confidence interval [CI], 3.6-9.0), indistinct soft or reticular drusen (23.2% vs 0.4%; RR, 9.9; 95% CI, 6.4-15.4), total drusen area of half the disc area or more (31.4% vs 0.6%; RR, 13.5; 95% CI, 8.0-22.8), and hyperpigmentation (14.4% vs 0.5%; RR, 8.0; 95% CI, 5.4-11.9). After adjusting for age, sex, and smoking status, eyes with these signs at baseline had a high likelihood of developing AMD. Eyes with Age-Related Eye Disease Study categories 3 and 4 were 5 times more likely to develop AMD compared with eyes in categories 1 and 2. CONCLUSION: This study quantifies the 5-year risk of AMD in eyes with macular drusen and hyperpigmentation.

Aged↗

Computer-assisted measurement of retinal vessel diameters in the Beaver Dam Eye Study: methodology, correlation between eyes, and effect of refractive errors.

OBJECTIVE: Narrowed retinal arterioles may independently predict cardiovascular disease. We describe a computer-assisted method to measure retinal vessel diameters from digitized fundus photographs in a large population, and examine the correlation of retinal vessel diameters between eyes and whether refractive errors affect these measurements. DESIGN AND POPULATION: Population-based, cross-sectional study in Beaver Dam, Wisconsin (n = 4926; age, 43-84 years). METHODS: Retinal photographs were digitized, and all arterioles and venules located in an area 0.5 to 1 disc diameter from the optic disc were measured with the aid of computer software. MAIN OUTCOME MEASURES: Summary of retinal arteriolar and venular diameters, and the ratio of their diameters (arteriole:venule ratio [AVR]). RESULTS: Correlation between right and left eyes was substantial for retinal arteriolar diameters (Pearson correlation coefficient, rho = 0.71) and venular diameters (rho = 0.74), and moderate for the AVR (rho = 0.49). The inverse association of higher blood pressure and smaller retinal arteriolar diameters was similar using data from either one eye or two eyes; arteriolar diameters decreased by 4.1 microm (right eyes), 4.0 microm (left eyes), and 4.0 microm (mean of both eyes) with each 10-mmHg increase in mean arterial blood pressure. A myopic refraction was associated with smaller retinal vessel diameters; arteriolar diameters decreased by 2.8 microm and venular diameters by 3.3 microm with each -1.0-diopter shift towards myopia. However, the pattern and strength of the association of blood pressure and retinal vessel diameters were not altered by variations in refractive errors. CONCLUSIONS: There is good correlation of retinal vessel diameters between eyes. A myopic refraction is associated with smaller retinal vessel diameters. The association of retinal arteriolar diameters and blood pressure seems similar using data from either one eye or two eyes, and is minimally affected by refraction. These data suggest that measurement of retinal vessel diameters from one eye without regard to its refractive status may provide adequate information indicative of a person's retinal vessel caliber if information from two eyes and refraction is unavailable.

Adult↗

Self-moved target eye tracking in control and deafferented subjects: roles of arm motor command and proprioception in arm-eye coordination.

1. When a visual target is moved by the subject's hand (self-moved target tracking), smooth pursuit (SP) characteristics differ from eye-alone tracking: SP latency is shorter and maximal eye velocity is higher in self-moved target tracking than in eye-alone tracking. The aim of this study was to determine which signals (motor command and/or proprioception) generated during arm motion are responsible for the decreased time interval between arm and eye motion onsets in self-moved target tracking. 2. Six control subjects tracked a visual target whose motion was generated by active or passive movements of the observer's arm in order to determine the role played by arm proprioception in the arm-eye coordination. In a second experiment, the participation of two subjects suffering complete loss of proprioception allowed us to assess the contribution of arm motor command signals. 3. In control subjects, passive movement of the arm led to eye latencies significantly longer (130 ms) than when the arm was actively self-moved (-5 ms:negative values meaning that the eyes actually started to move before the target) but slightly shorter than in eye-alone tracking (150 ms). These observations indicate that active movement of the arm is necessary to trigger short-latency SP of self-moved targets. 4. Despite the lack of proprioceptive information about arm motion, the two deafferented subjects produced early SP (-8 ms on average) when they actively moved their arms. In this respect they did not differ from control subjects. Active control of the arm is thus sufficient to trigger short-latency SP. However, in contrast with control subjects, in deafferented subjects SP gain declined with increasing target motion frequency more rapidly in self-moved target tracking than in eye-alone tracking. 5. The deafferented subjects also tracked a self-moved target while the relationship between arm and target motions was altered either by introducing a delay between arm motion and target motion or by reversing target motion relative to arm motion. As with control subjects, delayed target motion did not affect SP latency. Furthermore, the deafferented subjects adapted to the reversed arm-target relationship faster than control subjects. 6. The results suggest that arm motor command is necessary for the eye-to-arm motion onset synchronization, because eye tracking of the passively moved arm was performed by control subjects with a latency comparable with that of eye-alone tracking of an external target. On the other hand, as evidenced by the data from the deafferented subjects, afferent information does not appear to be necessary for reducing the time between arm motion and SP onsets. However, afferent information appears to contribute to the parametric adjustment between arm motor command and visual information about arm motion.

Adult↗

Statistics in ophthalmic research: two eyes, one eye or the mean?

BACKGROUND: Ophthalmic data, while different among individuals, are usually similar between fellow eyes of the same individual. This study was designed to illustrate alternative approaches to account for the correlation between fellow eyes. This is important for making inferences using data from both eyes. METHODS: With the use of a real data set from a population-based study, we described the distribution of intraocular pressure (IOP) by estimating the mean and standard deviation (SD) and evaluated the potential risk factors of higher IOP based on the regression method. The units of observation studied were of both eyes, right eye only, left eye only, the eyes with higher IOP and the mean value of both eyes. Furthermore, the generalized estimating equation (GEE) method was used to account for the correlation between fellow eyes in the regression analysis. Results and inferences from the different approaches were compared. RESULTS: The analysis included all the eyes, providing the largest sample size and unbiased estimates of the mean and SDs. There were some discrepancies among different approaches in the regression analysis. The GEE method simultaneously evaluated the effects of both eyes, and increased precision and enhanced inferences. CONCLUSIONS: Inconsistent results among different ophthalmic studies result from variations in not only study design and courses but also statistical methods. Making the best use of appropriate statistical techniques, which account for between eye correlation, provides valid statistical inferences.

Blood Pressure↗

[Difficulty in eye opening following left hemispheric infarction-- causative lesion and pathophysiology of abnormalities of the eye and eyelids movements].

We reported a patient suffering from difficulty in eye opening following left hemispheric infarction. A 78-year-old left-handed woman with atrial fibrillation had an acute onset of right hemiparesis and difficulty in eye opening. On admission, mild disorientation, vertical gaze palsy, right homonymous hemianopia, anosognosia of right hemiparesis, agnosia of right side of the body and forced grasping reflex of the left hand were seen. She was aware of her difficulty in opening her eyelids. Vertical saccadic eye movements were absent to command but when her head was free to move, the vertical saccadic eye movements improved that may suggest oculomotor apraxia. Bell's phenomenon was absent, and optokinetic responses were normal. Aphasia and facial apraxia were not seen. Brain CT and MRI demonstrated infarction in the territory of the anterior divisions of the left middle cerebral artery which includes the inferior frontal gyrus, middle frontal gyrus, fronto-parietal operculum and temporal operculum. SPECT disclosed hypoperfusion area in the left frontal lobe. No lesion was seen in the midbrain and pons. On the basis of these findings, cerebral emboli of the divisions of the left middle cerebral artery were diagnosed. Until about 11th days from onset, she could not open her eyelids by our verbal commands or even voluntarily, and showed paradoxical contraction of the bilateral orbicularis oculi muscles by verbal commands to open her eyes or when her eyes were forcedly opened by hands. After the 12th days from the onset, she became to be able to open her eyes voluntarily when she was asked to count the number of fingers presented in front of her face and when her families called her, but she could not open her eyes by verbal commands, which may be characteristic of apraxia of eyelid opening. She also had bilateral blephaloptosis when she opened her eyes. Considering this case together with previous reports, embolic lesion of the left cerebral hemisphere including the frontal eye field area and its adjacent areas which may be involved in higher control of eye lid movements and supranuclear vertical gaze movements was thought to cause difficulties in eye opening and vertical gaze palsy.

Aged↗

The epidemiology of serious eye injuries from the United States Eye Injury Registry.

BACKGROUND: Trauma remains a major problem throughout the world. The prognosis of severe eye injuries is commonly bleak. This paper focuses on the epidemiology of eye trauma, the role of ocular epidemiology, and identification and reduction of risk factors. METHODS: An analysis of the first 8,952 patients reported with severe eye injuries, defined as those eye injuries resulting in permanent and significant (measurable and observable on routine eye examination) structural and/or functional changes to the eye, from the United States Eye Injury Registry as of 31 July 1998. RESULTS: The age of patients entered was from the 1st year of life to 103 years. Fifty-eight percent of those injured were less than 30 years of age. The male to female ratio was 4.6:1, reaching 7.4:1 in the fourth decade of life. Almost half of the injuries involved the retina, and 77% of the injured eyes required one or more surgical procedures, including a large proportion which have undergone vitreoretinal surgical procedures. CONCLUSION: Injuries remain the most serious public health problem facing developed nations. Yet, a persistent inadequacy exists both in the standardized documentation of eye injuries and in their treatment. With appropriate surgical and medical intervention, a majority of the reported injured eyes recovered functional levels of visual acuity. It appears that glasses, including prescription glasses and even non-prescription sunglasses, can offer measurable protection which results in a lower incidence of severe eye injuries to those wearing glasses.

Adolescent↗

Shotgun eye injuries. Ocular risk and eye protection efficacy.

BACKGROUND: Little is known about the efficacy of shotgun eye protection. Shotguns can easily propel pellets with enough energy to penetrate the human eye, and a large percentage of shotgun eye injuries occur during shotgun sports such as hunting, trap, skeet, and sporting clays. Many of these injuries are preventable with proper eye protection. Although it is known that polycarbonate is the best lens material for shotgun eye protection, there has been no research that addresses the vision protective system design and its influence on eye protection. METHODS: A field study was performed during which shotshells were fired at 1:1 scale photographs of human faces to determine the risk of ocular trauma. The protective efficacy of three types of polycarbonate protective eye wear (standard industrial safety glasses with snap-on side shields, wrap-around racket sport glasses, and three-piece glasses with integral side shields) was tested by firing shotshells at them at various distances. Both frontal and side protection was evaluated. RESULTS: Results showed that the eye is at a high risk (55% to 100%) of being hit with shot pellets at ranges of 15 to 40 yards. It also was determined that the protective eye wear will give good frontal eye protection from shotgun pellets but integral side shields and a headband are necessary to obtain adequate side protection. CONCLUSION: These findings, coupled with the poor visual prognosis of ocular shotgun injuries, indicate that polycarbonate protective eye wear with integral side shields and headbands should be worn by all involved with shotgun sports.

Eye Injuries, Penetrating↗

Molecular genetic analysis of Drosophila eyes absent mutants reveals an eye enhancer element.

The eyes absent (eya) gene is critical for normal eye development in Drosophila and is highly conserved to vertebrates. To define regions of the gene critical for eye function, we have defined the mutations in the four viable eya alleles. Two of these mutations are eye specific and undergo transvection with other mutations in the gene. These were found to be deletion mutations that remove regulatory sequence critical for eye cell expression of the gene. Two other viable alleles cause a reduced eye phenotype and affect the function of the gene in additional tissues, such as the ocelli. These mutations were found to be insertion mutations of different transposable elements within the 5' UTR of the transcript. Detailed analysis of one of these revealed that the transposable element has become subject to regulation by eye enhancer sequences of the eya gene, disrupting normal expression of EYA in the eye. More extended analysis of the deletion region in the eye-specific alleles indicated that the deleted region defines an enhancer that activates gene expression in eye progenitor cells. This enhancer is responsive to ectopic expression of the eyeless gene. This analysis has defined a critical regulatory region required for proper eye expression of the eya gene.

5' Untranslated Regions↗

Eyeless initiates the expression of both sine oculis and eyes absent during Drosophila compound eye development.

The Drosophila Pax-6 gene eyeless acts high up in the genetic hierarchy involved in compound eye development and can direct the formation of extra eyes in ectopic locations. Here we identify sine oculis and eyes absent as two mediators of the eye-inducing activity of eyeless. We show that eyeless induces and requires the expression of both genes independently during extra eye development. During normal eye development, eyeless is expressed earlier than and is required for the expression of sine oculis and eyes absent, but not vice versa. Based on the results presented here and those of others, we propose a model in which eyeless induces the initial expression of both sine oculis and eyes absent in the eye disc. sine oculis and eyes absent then appear to participate in a positive feedback loop that regulates the expression of all three genes. In contrast to the regulatory interactions that occur in the developing eye disc, we also show that in the embryonic head, sine oculis acts in parallel to eyeless and twin of eyeless, a second Pax-6 gene from Drosophila. Recent studies in vertebrate systems indicate that the epistatic relationships among the corresponding vertebrate homologs are very similar to those observed in Drosophila.

Animals↗